1. Field of the Invention
The present invention generally relates to the field of radio telecommunication apparatus such as battery-powered mobile and portable telephones and, more particularly, to an apparatus and method for reducing power consumption in a radio telecommunication apparatus used in a radio telecommunication system in which a communication link is established using a plurality of radio channels.
2. Description of the Relevant Art
Various types of radio telecommunication apparatus have been developed recently. One type is generally referred to as a mobile radio telephone. The mobile radio telephone, which may be installed in a vehicle such as a car, a train, a ship, an airplane or the like, comprises (1) a transceiver unit with an antenna and telephone unit including a handset and (2) a base unit. The transceiver and base are independent units which are coupled to each other by signal lines. The mobile radio telephone is powered by the vehicle battery.
A second type of radio telephone is generally referred to as a portable telephone. Portable telephones are further divided into two groups: a transportable type and a hand-held type. In the transportable type, the transceiver unit is incorporated into the main telephone unit and an antenna is attached thereto. Thus, a user may carry the transportable telephone. In the hand-held type, all of the components are incorporated in a single unit which may be held in the user's hand. Like the mobile unit discussed above, the transportable and hand-held telephones are battery powered.
The above-described telecommunication apparatus are used in radio telecommunication systems such as cellular radio systems. In cellular radio systems, a large geographical area is serviced by one or more base stations by dividing the area into a plurality of small zones or cells. The zones or cells define a service area in which a mobile telephone may establish a communication link with another party. Outside the service area, however, the mobile telephone may not be served by the serving cellular radio system.
It is desirable to reduce power consumption in a radio telecommunication apparatus since the battery installed therein or in the vehicle has limited power capacity. As an example, in paging devices and systems, power consumption is reduced by dividing all of the pagers in a paging system into a plurality of groups. Power supplied to the radio section of a particular pager is periodically switched on and off such that only paging signals directed to the group to which the particular pager belongs are received. This technique for reducing power consumption of the battery is generally referred to as a group battery saving technique.
However, it is difficult to apply the group battery saving technique to the above-described radio telecommunication system since a plurality of radio channels are used in radio systems. In addition, radio telecommunication apparatus such as mobile telephones are not divided into groups. Further, radio telecommunication apparatus not only recieve radio signals but also transmit radio signals over one or more radio channels.
Therefore, in prior art radio telephone apparatus, power is continuously supplied to the radio telephone after an associated power switch is switched on.
Commonly assigned U.S. patent application Ser. No. 07/316,922, filed Feb. 28, 1989 now U.S. Pat. No. 5,033,111 entitled "Radio Telecommunication Apparatus" discloses an improved radio telecommunication apparatus capable of conserving battery power by controlling the power supplied to the transmitter.